1. Field of the Invention
The invention discloses a new class of compounds that absorbs ultraviolet (UV) radiation, being produced by two embodiments. By a first embodiment, the ultraviolet-absorbing compound is derived from at least one first reactant being a UV absorber having a carbon-nitrogen triple bond and at least one second reactant having amine functionality. Alternatively, by a second embodiment the ultraviolet-absorbing compound is derived from at least one first reactant being a UV absorber with amine functionality and at least one second reactant comprising a carbon-nitrogen triple bond. In both embodiments of the invention, the second reactant may be a small molecule, a monomer, a macromolecule, a biomolecule, or a polymer.
The invention's ultraviolet-absorbing compounds are directed toward formulations and applications in any art that serve to protect against UV radiation. Exemplary uses of the ultraviolet-absorbing compounds are in adhesive, agriculture, cleaning/polishing, coating, containers, encapsulation, fragrances, imaging, hoses/tubing, household/industrial/institutional, medical, membrane, molded parts, oilfield, packaging, personal care, personal protective equipment, pharmaceutical, printing, veterinary, and wood-care applications. Highly preferred uses of the ultraviolet-absorbing compounds are in personal care and performance chemicals.
2. Description of Related Art
It is now generally accepted that ultraviolet (UV) radiation can be a serious health hazard. Even a limited exposure to solar radiation can cause short- and long-term skin damage, such as erythema, burns, wrinkles, lentigo (“liver spots”), skin cancers, keratotic lesions, and other cellular changes. There is a greater risk for developing such conditions for those who send prolonged time in the sun, such as for their occupation or during recreation.
UV radiation is just one portion of the electromagnetic spectrum, with wavelengths from about 100 nm and about 400 nm, and is further divided into three subregions. UV-A radiation, from about 320 nm to about 400 nm, has the longest wavelength within the UV spectrum, and consequently is the least energetic. While UV-A rays can induce skin tanning, they are liable to induce adverse changes as well, especially in the case of sensitive skin or of skin which is continually exposed to solar radiation. In particular UV-A rays cause a loss of skin elasticity and the appearance of wrinkles, leading to premature skin aging. UV-B rays have shorter wavelengths, from about 290 nm to about 320 nm, and their higher energy can cause erythema and skin burns which may be harmful. The third subgroup, UV-C has the shortest wavelengths, from about 200 nm to about 290 nm, and the highest energy. The Earth's ozone layer effectively filters much UV-C radiation from reaching the ground. Nonetheless, UV-C rays can be generated from tanning bed devices.
In addition to harming the skin, UV radiation can injure the hair, resulting in color changes (especially for color-treated hair), embrittlement, and a loss in aesthetics (e.g., shine, manageability).
UV radiation damage is not limited to the skin and hair, as inanimate objects exposed to solar radiation can experience changes related to color, hardness, and structural integrity, which can contribute to aesthetical and functional deterioration.
Thus, there is the very real and demanding need for compositions that protect the skin, hair, and objects from UV rays, especially UV-A and UV-B radiation. Of special interest are compositions that provide UV-spectrum protection from both UV-A, UV-B, and UV-A and UV-B radiation.
Para-aminobenzoic acid (PABA) exhibits a common trait shared with many UV absorbers/filters. The molecule possesses both electron withdrawing and electron accepting groups, providing resonance delocalization that coincides with the absorbed energy of UV radiation:

However, PABA is a highly polar molecule, making it water soluble, and giving it a low persistence, meaning that it is not highly retained on the skin after swimming or perspiring. In addition, due to extensive intermolecular bonding, PABA exists as a solid, which may further complicate its formulation. Thus, there exists the need to improve the persistence of UV absorbers, especially those that are water-soluble, and to provide formulation flexibility.
UV absorbers may exhibit photolability, in which the absorbed energy causes photodegradation and/or photoreactivity, and thus reduce its efficacy. Such photolability may result from irreversible isomerisms (i.e., keto-enol tautomerism and cis-trans isomerism), photocleavage, and/or photoaddition, and may be formulation sensitive, (e.g., blends of avobenzone and octinoxate). Examples of photolabile UV absorber include, without limitation: avobenzone, PABA derivatives, cinnamates, and dibenzoyl methane derivatives, all of which degrades over time, and reduce UV protection. Hence, there exists a need to stabilize UV absorbers from photodegradative effects.
Additionally, there exists the need to enhance the efficacy of UV absorbers without increasing their content in the formula, since a maximum addition level frequently is regulated. This efficacy need is especially important for avobenzone, a highly effective UV-A absorber. Avobenzone is subject to keto-enol isomerization due to formulation dependencies (e.g., solvent, other UV absorbers):

The enol tautomer (left) has its maximum absorbance at 357 nm, which identifies it as a UV-A absorber. Unfortunately, avobenzone is subject to bimolecular reactions (e.g., via cleavage mechanisms) that alter the molecule's structure and decrease its effectiveness as an UV absorber. Hence, an effective method is needed for stabilizing labile UV absorbers like avobenzone in order to enhance their efficacy without increasing their addition level.
Finally, there exists an important need to reduce the migration and skin penetration effects of UV absorbers. For example, octocrylene is a clear, viscous liquid that provides effective protection from UV-A and UV-B radiation. Yet, octocrylene can penetrate the epidermis, where it can act as a photosensitizer and indirectly lead to free-radical damage (Hanson et al., 2006). The desirable protecting properties of UV absorbers like octocrylene would be enhanced if their skin penetration were reduced and/or eliminated.
Amine-containing compositions that stabilize UV absorbers are known in the prior art. For example, stabilized polyolefin-based polymers are taught in U.S. Pat. No. 4,104,248 having the general formula:
wherein R1, R2, R3, and R4 are equal to or different from each other and are C1-C4 alkyl groups, R5 is hydrogen or a C1-C4 alkyl group, A is a C2-C10 alkylene group, B is a divalent aliphatic, cycloaliphatic, aromatic, or alkylaromatic radical that may contain hetero atoms such as O, S, N, and P, and n is a whole number between 2 and 1000. Compositions of that invention find application in yarns, raffia, ribbons, and shaped articles.
Polyalkylenenaphthalene-2,6-dicarboxylates having reduced fluorescence are provided in U.S. Pat. No. 6,001,952.
U.S. Pat. No. 6,492,455 discloses aqueous solutions comprising the reaction product of a C6+ alpha-olefin/malcic anhydride copolymer with a polyfunctionalized secondary or tertiary amine. The disclosure includes a water-proof sunscreen composition wherein a reaction product of the '455 invention is mixed with benzophenone-3 and octocrylene; the former UV absorber is not covalently bonded to the polymeric reaction product.
Functionalized poly(alpha-olefin-maleic anhydride) polymers are the subject of application PCT/EP2007/051697. This functionalized copolymer has the structure:
wherein —X— is —O— or —NH—, and —X—R2— is a functional radical selected from a group that includes natural molecules that are UV absorbers, such as tannins, flavonoids, thymol, caffeic acid esters, and vitamin E.
UV-containing polymers are disclosed in the prior art, primarily for industrial applications. Stabilizers for synthetic resins produced from monochlorocyanurates are provided in U.S. Pat. No. 4,698,381. Polymers to eliminate laundry dye transfer are described in U.S. Pat. No. 6,008,316. Ink compositions are provided in U.S. Pat. Nos. 6,059,870; 7,084,189; and U.S. Pat. No. 7,435,291.
U.S. Pat. No. 4,882,412 describes molded plastic compositions produced from the copolymerization of a benzopyran. The compounds are essentially colorless and are directed to untinted packaging materials. Water-dispersible polymeric compounds containing an optical brightener are provided in U.S. Pat. No. 6,150,494 for use in inks, paints, and film forming compositions, especially those compositions for security marking or tagging. The optical brightener comprises at least one polyester reactive group.
Water-borne acrylic polymers are taught in U.S. Pat. No. 6,150,494 and WO 2000/078864 for surface coatings and colorants produced from a vinyl ester monomer and a polymeric fluorescent compound comprising repeating units of residues of: (a) a monomer comprising a dicarboxylic acid or ester, (b) a monomer comprising a diol, diamine or a mixture thereof, (c) a monomer comprising at least one sulfonate group and at least one polyester reactive group, and (d) a monomer comprising an optical brightener agent having at least one polyester reactive group. Personal care applications are not disclosed.
Despite advances in UV absorber technology and formulation development, there remains an unmet need for novel UV absorber compositions, especially those that can provide broad UV-spectrum protection, provide improved water-proofness, stabilize UV absorbers from photodegradative effects, and/or reduce skin penetration tendency. Surprisingly, the ultraviolet-absorbing compounds disclosed address these needs.